content: /*
   * Copyright 2017 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package hu.akarnokd.reactive4javaflow.impl.util;
  
  import hu.akarnokd.reactive4javaflow.impl.PlainQueue;
  
  import java.util.concurrent.atomic.AtomicReference;
  
  public final class SpscOneQueue<T> extends AtomicReference<T> implements PlainQueue<T> {
      @Override
      public boolean offer(T item) {
          if (getAcquire() == null) {
              setRelease(item);
              return true;
          }
          return false;
      }
  
      @Override
      public T poll() {
          T v = getAcquire();
          if (v != null) {
              setRelease(null);
          }
          return v;
      }
  
      @Override
      public boolean isEmpty() {
          return getAcquire() == null;
      }
  
      @Override
      public void clear() {
          setRelease(null);
      }
  }
  